Scale on an apparatus for measuring displacement

ABSTRACT

A scale on an apparatus for measuring displacement is enclosed which comprises a scale member having a plural of rectangular gratings arranged with periodic pattern on the glass epoxy substrate and the like, a coating layer covered on the side of the scale member which a plural of the rectangular gratings are formed, a scale cover (film layer) which functions as a protective layer and a scale forming material bonded to the outer portion of the coating layer through an adhesive layer so as to keep contaminant, oil or particles from intruding between the rectangular grating and the adhesive layer such as an adhesive tape and the like.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a scale on an apparatus for measuring displacement and more particularly to a scale providing a high environmental resistance on an apparatus for measuring displacement

[0003] 2. Prior Art of the Invention

[0004] A scale on an apparatus for measuring displacement, for example, for an electronic caliper disclosed in U.S. Pat. No. 5,973,494 to Karl G. Mareliez et al is bonded to the top surface of a slider's beam assembly (described as P in FIG. 4 of the present invention) the prior art as shown in FIG. 4, the scale includes generally an elongated printed circuit board. A plural of rectangular gratings 12 are spaced apart along the printed circuit board in a periodic pattern on a glass-epoxy substrate 11. The scale includes also a scale cover 30 which is deposited to the top surface of a plural of rectangular gratings 12 by an such as an adhesive tape and the like. The scale cover 30 serves as a protector for the adhesive layer 20. The protector 30 can also include a printed marking.

[0005] In such a conventional scale used for the apparatus for measuring displacement, since the top surface side of the scale substrate 11 are formed with raised or portions by bonding the rectangular grating 12 thereon and thereby act to provide an imperfect contact with the scale cover 30. Consequently contaminated coolant and oil can find their way between the scale member 10 and the scale cover 30 and intrude into the gap therebetween and the scale cover 30 is easily peeled from the adhesive layer 20. Thereby contaminated coolant and oil cause measurement errors.

[0006] Furthermore when such a scale used at conventional shop, coolant and oil may potentially intrude into the gap between the scale member 10 and the scale cover 30. In some type of oil, the components of no water-solvent coolant containing chlorin and sulfur may causes chemical reaction with the rectangular grating 12 made from copper to make them corroded, to disrupt the rectangular grating 12 and to result in detection error.

[0007] This invention has been made in view of the above-described state in the prior art, and has for its object to provide a scale for measuring displacement having a significant resistance to environment such that provides a great reliability in the harmful industrial environment.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The preferred embodiments of the invention will be described in detail with reference to the following figures, wherein:

[0009]FIG. 1 shows a crossed view representative of a scale having a plural of rectangular gratings on an apparatus for measuring displacement of the first embodiment.

[0010]FIG. 2 shows a crossed view representative of a scale having a plural of rectangular gratings on an apparatus for measuring displacement of the second embodiment.

[0011]FIG. 3A shows a schematic view representative of a scale of an electrostatic capacitance-type encoder and an optical-type encoder on apparatus for measuring displacement of the present invention.

[0012]FIG. 3B shows a schematic view representative of a scale of magnetic-type encoder on apparatus for measuring displacement of the present invention.

[0013]FIG. 4 shows a crossed view representative of a scale on an apparatus for measuring displacement of the prior art.

SUMMARY OF THE INVENTION

[0014] In one aspect of the present invention, a scale on the apparatus for measuring displacement is provided. The scale comprises a scale member including a plural of the rectangular grating formed on top surface of the scale substrate, a coating layer covering the side on which the rectangular grating are formed, and a scale cover covering with a bonding layer on the coating layer which covers on the rectangular grating formed on the scale substrate.

[0015] According to the present invention, since the coating layer is covered at least on the side of the scale substrate which the rectangular grating are formed, it prevents coolant and oil and the like from intrude into a gap between the scale electrode and the scale member. As result, the scale of the present invention can sufficiently provide the reliability on an apparatus for measuring distance no matter how it is used in a harmful contaminate-filled environment.

[0016] Material having a high solvant resistance, such as polyimid and epoxy based coating material and the like is suitable for the coating layer. The contacting portion of the coating layer with the scale cover is desirable to be cleaned and activated by plasma radiation so as to enhance adhesiveness between the coating layer and the scale cover. The material which can be coated at low temperature, for example, ultraviolet hardening agent is desirably used for the coating layer such that the rectangular grating can prevents from deforming. If the scale member is entirely surrounded with the coating layer, a higher protection from contaminant is further provided.

[0017] Referring to the figures, the preferred embodiment of the present invention will be explained next. FIG. 1 shows a crossed view representative of a scale on an apparatus for measuring displacement of the first embodiment. The scale comprises a scale member 10 having a plural of rectangular gratings arranged with periodic pattern on the glass epoxy substrate 11 and the like, a coating layer 40 covered on the side of the scale member 10 which a plural of rectangular gratings 12 are formed, a scale cover (film layer) 30 which functions as a protective layer and a scale forming material bonded to the outer portion of the coating layer 40 through an adhesive layer 20 so as to keep contaminant or oil from intruding between the rectangular grating 12 and the adhesive layer 20 such as an adhesive tape and the like.

[0018] The scale comprises the coating layer 40 cleaned, activated and made rough by radiating plasma after it is coated on the side of the scale which the rectangular grating 12 are deposited. Further bonding the coating layer to the scale cover 30 enhances adhesive strength between the scale cover 30 the coating layers 40, and prevent the scale cover 30 from be peeled along with provided smooth flatness on the surface of the scale member 10.

[0019] Polyimid and other epoxy based having a high solvent resistance is suitable for the material for coating layer 40. If a coating work is performed at high temperature, the rectangular grating are potentially deformed (elongation) and provided with accuracy error. In order to solve such a problem, UV coating layer 40 such as UV ink for a screen-typed printing machine, for example “SEIKA BEAM” manufactured by DAINICHI SEIKA KOUGYO and the like, may be also used.

[0020]FIG. 2 shows a crossed view representative of a scale of apparatus for measuring displacement of the second embodiment. This embodiment shows that the coating layer covers not only on the side of the scale member 10 which a side of rectangular grating 12 are deposited, but also reverse side of it. In this case, in order to obtain a high adhesion on bonding, the scale cover 30 is desirable to bond on the adhesive layer 20 after the reverse side of the rectangular grating 12 is performed by plasma radiation for a rough surface thereon.

[0021] As described above, since the coating layer covers not only on the side of the scale member 10 which a side of the rectangular grating 12 are deposited, but also entirely surrounding the scale member including the electrodes and the scale substrate, it prevent a harmful contaminant or oil from intruding between the rectangular grating 12 and the adhesive layer 20. As a result, the present invention brings a great advantage that provides the reliability of a scale of apparatus for measuring displacement even when operating in the harmful environment contaminated by coolant and the like.

[0022] In an apparatu for measuring displacement, the rectangular grating is composed of signal transferring portions and signal non-transferring portions which are arranged at predetermined pitch.

[0023] In the encoder used for an capacitance type apparatus for measuring displacement, the signal transferring portion is electric signal transferring portion that uses capacitance coupling (FIG. 3A). In the encoder used for an optical type apparatus for measuring displacement, the signal transferring portion transmits or reflects on an optical encoder (FIG. 3A). In the encoder for a magnetic measuring displacement, the signal transferring portion is a magnetic signal transferring portion that uses magnetic coupling (FIG. 3B).

[0024] While aspects of the present invention have been particularly shown and described with reference to the preferred embodiment above, it will be understood by those skilled in the art that various additional embodiments may be contemplated without departing from the spirit and scope of the present invention. 

What is claimed is:
 1. A scale on apparatus for measuring a displacement, comprising: a scale member including a plural of gratings formed at least on the top surface of the scale substrate, a coating layer covering the side on which said grating are formed, and a scale cover covering with a bonding layer on said coating layer which covers on said grating formed on said substrate.
 2. A scale on apparatus for measuring a displacement according to claim 1 wherein said coating layer is radiated by plasma to its facing surface to the scale cover for rough surface thereon.
 3. A scale on apparatus for measuring a displacement according to claim 1 wherein said coating layer is Polyimid and other Epoxy system material.
 4. A scale on apparatus for measuring a displacement according to claim 1 wherein said coating layer is an ultraviolet hardening agent.
 5. A scale on apparatus for measuring a displacement according to claim 1 wherein said coating layer is surrounded entirely the scale substrate
 6. A scale on apparatus for measuring a displacement according to claim 1 wherein said grating is composed of signal transferring portions and signal non-transferring portions.
 7. A scale on apparatus for measuring a displacement according to claim 1 wherein said grating is composed of a magnetic signal transferring portions and magnetic signal non-transferring portions.
 8. A scale on apparatus for measuring a displacement according to claim 1 wherein said grating is composed of light transmitting portions and light non-transmitting portions. 